Agricultural drought

Also called: Soil moisture drought · Topic: Natural Hazards and Disaster Management in India · NCERT: Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"

Meaning

Agricultural drought (also called soil moisture drought) is a shortage of soil moisture (water held in the soil) during the crop season, so crops wilt and fail. It is the stage where a rain shortage starts to hurt farmers. It causes food shortage, job loss and distress migration. NCERT does not count an area as drought-prone if more than 30% of its gross cropped area is irrigated.

Explanation

How it forms

• Rain fails first (meteorological drought).

• Too little rain falls, or it is badly spread over the season.

• Then the soil dries.

• Evapotranspiration (water lost from soil by evaporation, plus water given off by plants) keeps taking water out of the soil.

• High heat increases evaporation, so the soil dries faster.

• Then crops wilt and fail.

• Plant roots cannot get enough water from the dry soil.

• The result is crop failure, food shortage and lost farm work.

• It is a slow-onset hazard. It builds up over weeks and months. It does not strike suddenly like a cyclone or an earthquake.

Its place in the drought chain

• Meteorological drought: rain fails. This comes first.
• Agricultural drought: soil moisture runs short and crops fail. It follows a rain shortage during the crop season.
• Hydrological drought: over months, rivers, tanks, reservoirs and wells run low.
• Ecological drought: forests, grasslands and wetlands stop being productive because of water stress.

Conditions and the irrigation rule

• Gross cropped area: all the area sown in a year. Land sown twice is counted twice.
• The 30% rule (NCERT):
• Irrigation brings water to the soil even when rain fails.

• So an area with more than 30% of its gross cropped area irrigated is not counted as drought-prone.

• Conditions that make it worse:

• an uncertain monsoon
• thin soils on a hard rock base, which hold little water (for example, Bundelkhand)
• groundwater pumped out faster than rain can refill it

How it is measured: Manual for Drought Management (2016, updated 2020)

• Step 1: Mandatory indicators (Trigger-1) [2]
• rainfall deviation (how far rain is from normal, in %) or SPI (Standardised Precipitation Index: a score of how unusual the rain is compared with past rain)

• plus a dry spell: usually 4 weeks, 3 weeks on light soils and 2 weeks on sandy soils [2]

• Step 2: Impact indicators (Trigger-2). The state picks any 3 of 4 [2]:

• crop situation, such as sown area compared with normal
• remote-sensing vegetation indices: NDVI (how green the plants are), NDWI (water in plants) and VCI (Vegetation Condition Index)
• soil-moisture indices

• hydrological indices: SFDI (stream flow), GWDI (groundwater) and RSI (reservoir storage)

• Grading [2]:

• severe if 2 of the 3 chosen impact indicators are in the severe category

• moderate if 2 of the 3 are in the moderate category

• Step 3: Ground truthing (checking on the ground) [2]

• checks are done in a random 10% of affected villages, preferably with a smartphone app
• a crop loss of 33% or more qualifies for a drought declaration

Where it occurs

• Extreme drought zone: most of Rajasthan west of the Aravalis, which covers the Marusthali (Thar desert), and Kachchh (Gujarat). Jaisalmer and Barmer get under 90 mm of rain a year.
• Severe drought zone: eastern Rajasthan, most of Madhya Pradesh, eastern Maharashtra, interior Andhra Pradesh and the Karnataka plateau, northern interior Tamil Nadu, southern Jharkhand and interior Odisha.
• Moderate drought zone: northern Rajasthan, Haryana, southern Uttar Pradesh, the rest of Gujarat, Maharashtra except Konkan, Jharkhand, the Coimbatore plateau (Tamil Nadu) and interior Karnataka.
• Chronic drought regions (drought comes back again and again):
• Marathwada (central Maharashtra) lies in the rain shadow of the Western Ghats. A rain shadow is the dry side of a mountain, away from the moist wind.

• Bundelkhand (southern Uttar Pradesh and northern Madhya Pradesh) has a hard rock base, thin soils and uncertain rain.

• Why central and western India is prone:

• The Western Ghats take most of the south-west monsoon rain, so the interior Deccan stays dry.

• Monsoon margins such as Rajasthan and Gujarat lie at the outer edge of the monsoon's reach. Rain there is low and very uncertain.

• Scale (NCERT): about 30% of India's area is drought-prone, affecting about 50 million people.

• Who declares and monitors it [2]:
• Drought is declared by state notification under the Drought Manual.
• Kharif drought is declared by 31 October (early declaration possible in August).
• Rabi drought is declared by 31 March (early declaration possible in November or December).
• Crop condition from satellites comes from MNCFC, NRSC and the State Remote Sensing Centres. Rainfall data comes from IMD.

• ICAR-CRIDA updates the District Agriculture Contingency Plans, and the Crop Weather Watch Group checks crops and weather every week.

• Area programmes: Drought Prone Areas Programme (DPAP), started 1973-74, and Desert Development Programme (DDP), started 1977-78.

Don't confuse with

• Meteorological drought: a shortage of rain, tested by IMD as seasonal rain more than 25% below normal (26-50% = moderate, more than 50% = severe). It comes before agricultural drought.
• Hydrological drought: a shortage of water in aquifers, lakes and reservoirs. It comes after meteorological drought, not at the same time. An aquifer is an underground layer of rock or sand that holds water.
• Ecological drought: a shortage of water for a natural ecosystem, not for crops. It can last even after the rain returns.
• Trinkal vs akal: akal is a shortage of food grain, which is the direct result of crop failure. Trinkal is a shortage of fodder (food for cattle). Trikal means all three shortages together: grain, fodder and water (jalkal).

Prelims Hooks

• An area with more than 30% of its gross cropped area irrigated is not counted as drought-prone (NCERT).
• Order of drought types: meteorological → agricultural → hydrological → ecological.
• NDVI, NDWI and VCI are satellite vegetation indices used to judge drought [2].
• Drought Manual: rainfall deviation or SPI, plus a dry spell, are mandatory. A crop loss of 33% or more qualifies for a declaration [2].
• Kharif drought is declared by 31 October. Rabi drought is declared by 31 March [2].
• Trap: the Coimbatore plateau and interior Karnataka are in the moderate zone. The Karnataka plateau and eastern Rajasthan are in the severe zone.

Mains Points

• Why agricultural drought is so common in India (GS-I/III):
• The monsoon is uncertain, and the rain-shadow interior and the monsoon margins are dry.
• Groundwater is pumped out faster than rain refills it, so irrigation cannot always save the crop.

• Marathwada, Bundelkhand and Rajasthan are hit again and again.

• Impacts:

• Crop failure leads to akal. Cattle suffer from trinkal and jalkal.
• People migrate in distress, food prices rise, and the poor and landless suffer most.

• Contaminated water spreads diseases such as gastroenteritis, cholera and hepatitis.

• Policy response, from relief to risk reduction (Sendai Framework, 2015-2030):

• The 2016/2020 Drought Manual uses satellites, soil-moisture indices and ground truthing, so declarations are faster and fairer. Funding comes from the NDRF for severe drought and the SDRF for moderate drought [2].
• States set aside 5-10% of RKVY flexi-funds in case of a bad monsoon [2].
• Long-term fixes include drought-resistant crops, MGNREGS ponds and check dams, and watershed development and rainwater harvesting under Jal Shakti Abhiyan: Catch the Rain [3].

Related concepts

• Drought
• Meteorological drought
• Hydrological drought
• Ecological drought
• Drought-prone areas of India
• Akal, trinkal, jalkal and trikal
• Drought mitigation

Read more

• Droughts: types, drought-prone India and mitigation